Here are a few tips to help tell if someone has opened/read your email:

1. Look at the email headers: Some emails may show the date and time of when the recipient opened the email. This information is found in the email headers and can be found by clicking on the options or details in the email.
2. Track the link clicks: Try embedding a link in the email and use a link tracking program to get notifications like Contact opened the email at 3:57 PM.
3. Request a read receipt: You can request an electronic read receipt from the recipient. The recipient will need to manually confirm that they acknowledge the receipt of the email.
4. Check the activity: Set up notification alerts through feeds, or you can use a software that has reports showing when the email was opened.